Process for shutting-down catalytic apparatus employed for the conversion of hydrocarbons



E. J. GOHR ET AL ,4 6 PROCESS FOR SHUTTING-DOWN CATALYTIC APPARATUSEMPLOYED FOR THE CONVERSION OF HYDROCARBONS Original Filed Dec. 30, 19423 Sheets-Sheet 2 268 Q 266 286 Ex/m usrsa. 284 J 292 ;sToA2AGE HOPPER.""gbzss M mentor s z w w Afiiorru E. J. GOHR ET AL 2,655,466 PROCESS FORSHUTTING-DOWN CATALYTIC APPARATUS FOR THE CONVERSION OF HYDR 42 EMPLOYEDOCARBONS Original Filed Dec. 30, 19

5 Sheets-Sheet 3 Patented Oct. 13, 1953 UNITED STATES PATENT OFFICEPROCESS FOR SHUTTING-DOWN CATA- LYTIC APPARATUS EMPLOYED FOR EsCONVERSION OF HYDROCAR- Edwin J. Gohr, New York, N. Y., and Homer Z.

Martin, Cranford, Charles E. Jahnig, Red Bank,

arlcs W. Tyson, Summit, and John M.

Graham, Plainfield, N. J., assignors to Standard Oil DevelopmentCompany, a corporation are Original application December 30, 1942,Serial No. 470 534 Divided and this application 1 Claim. (Cl. 19652)This invention relates to catalytic reactions in products. Theseparating means is provided h ch the a ys 's n powdered or finelydiwith a plurality of dip or return pipes of different vided form andmore particularly relates to the lengths to return the catalystparticles to the rea alytic tr atment or conversion of hydrocaractionzone when operating with difi'erent levels bone. 5 of catalyst in thereaction zone. The separated According to this invention the reactantsand reaction products in vapor form are then passed powdered catalystare maintained in a reaction to suitable equipment for the separation ofdezone which forms part of a larger vessel and the sired fractions.velocity of the vapor or gaseous reactants pass- In certain reactionsthe catalyst particles being through the reaction zone is so selectedthat come inactivated or spent and it is necessary to a level locatedbelow the top of the reaction zone. condition and flow into thestripping zone from forming the reaction zone, the spent catalyst ismixture passed through the regeneration zone.

catalyst particles. so selected to give a fluidized bed of catalyst.

The powdered catalyst is introduced into the The hot regeneratedcatalyst is withdrawn from bottom portion of the reaction zone and inthe the bottom of the regeneration zone and is intropreferred form ofthe invention the solid contact duced into a standpipe by means of whichit is r ataly t pa t s e at a relatively h h t returned to the reactionzone. The level. of the the reactants and to supply the heat ofreaction. amount of catal above the bottom of the vessel of which a partof the stripping gas passing from the stripping e e n ration gasesleaving the separating Where the level of fluidized catalyst in the allof the entrained catalyst particles from the small amount of catalystparticles is carried 0 into the hopper below the precipitator to makeregeneration to heatthe contact particles to the desired temperature andin such case heat is supplied to the regeneration zone by an auxiliaryburner or oil may be injected into the regenera Fig. 1 represents oneform or the invention which embodies the principles of the invention;Fig. 1A represents a continuation of Fig. l and includes storage hoppersand associated parts for receiving catalyst or contact particles fromthe,

reaction vessels shown in Fig. 1 when the unit is to be shut down;

Fig. 2 represents a detail partly in section showing the mixing chamberfor mixing the contacting agent and reactants;

Fig. 3 represents a vertical cross section taken substantially on line33 of Fig. 2, and

Fig. 4 represents a sectional view taken sub.- stanially on line 4-4 ofFig. 3 and showing nozzles for introducing the liquid feed into thepowdered catalyst or contact particles.

Referring now to the drawings and to Fig.1, the reference character itdesignates a line or pipe into which reactants are introduced throughlines H and l and catalytic material through line l2 as will be laterdescribed. The mixing of the liquid reactants and powdered. materialwill be hereinafter descri ed in greater detail. In certain reactionsthe reactants may be introduced at ordinary temperatures and the heatnecessary for preheating the reactants and for the reaction is sippliedby hot regenerated catalyst or contact particles. In the catalyticcracking of hydrocarbons or other conversion operation the oil feed maybe partly preheated. by passing through heat exchangers but insuiiicientheat is supplied to completely vaporize the oil feed or to supply theheat of reaction. Heat for vaporizing the oil and converting it issupplied by hot regenerated contact particles and no vaporizing furnacefor the oil or reactants is necessary. troduced into line ill are mixed.in a mixing zone l3 (Figs. 1, 2 and 3) with hot regenerated catalyst orcontact particles introduced into line W by means of line i2. As aresult the liquid reactants are vaporized. and raised to reactiontemperature and the resulting mixture is passed through line Hi to thedischarge end it of the pipe M which is flared. or cone shaped to give alarger area for distributing the mixture in the reaction zone. Thedischarge end of the line [4 is provided with a distribution plate l8which is provided with perforations for distrib ting the solid particlesand the vaporized or gaseous reactants as they are discharged into thereaction zone 22 formed in larger vessel 23.

Where the pipes in and H are of a relatively large diameter thereactants are mixed with the hot catalyst particles by means of aplurality of pipes or smaller lines to more evenly distribute thereactants into the catalyst or contact particles as will be hereinafterdescribed in greater deail.

The catalyst or contact particles and vaporized or gaseous reactantsafter being introduced into the reaction zone 22 are maintained thereinin a dry fluidized condition having a level indicated at 24. The solidparticles are maintained in a fluidized condition by selecting ormaintaining the velocity of the gases or vapors at a desired figure. Thelevel shown at 24 is included only for the purpose of illustration andthis level may be varied either to control the extent of the reaction orto carry out different reactions.

75 chamber 46.

' The reactants remain in contact with the solid or catalyst particlesfor the desired time-to eilect the desired reaction. The catalyst orcontact particles are maintained in a turbulent condition in a thereaction zone. and the reactants are contacted with the solid particles.A substantially uniform temperature is maintained throughout thefluidized bed of catalyst because of the fluidized condition of thesolid particles.

The reaction products in vapor form leave the fluidized catalyst bed andpass upwardly through a separating means 26 which is shown in thedrawing as a cyclone or multi-clone separating means. Preferably theseparating means is arranged in the upper portion of the reaction zoneor: vessel 22. Other separating means may be used. Theseparating means26 provides a means for separating dry entrained solid particles fromthe dry vaporous reaction products. The vaporous reaction products passthrough line 28 to a fractionating system. (not shown) or a system forseparating desired products. The separated solid particles are collectedin the hopper 32 associated with. the separating means and returned tothe catalyst bed in the reaction zone through one of a plurality ofreturn dip pipes.

As shown in the drawing, a longer return pipe 34 anda shorter returnpipe 35 are provided. The longer return pipe 34 is provided with a valve36 and the shorter return pipe 35 has a valve 42. As shown in thedrawing, the longer return pipe 34 extends into the bed of catalystbelow the level 24 and this return pipe is used where the catalyst bedis relatively shallow. Where the catalyst level 24 rises above theshorter return pipe 35, the shorter return pipe 35 is used to return thecatalyst to the catalyst bed.v The valve 38 is manually operated fromoutside the reactor to maintainv the pipe 34 substantially full ofcontact particles at all times when the longer pipe 34 is being usedduring the operation of the process.

When longer pipe 34 is used, valve d2 inshorter pipe 35 is closed. Whenthe shorter pipe 35 is used, valve 42. is manually operated from outsideP the reactor to maintain the pipe 35 -full of contact particles duringthe operation of the process and valve 36 in longer pipe 34 is closed.The extent of conversion may be controlled or changed by varying theheight of catalyst level 24 in the reaction zone 22. Similar returnpipes of different length may be used for returning catalyst from thecyclone separating means to the regeneration zone later to be described.

The vaporous reaction products leavin the separating means 26 contain asmall amount of entrained catalyst and are passed through line 28 andintroduced into suitable equipment for separating desired products orfractions from the reaction products. Heavier constituents are condensedand entrained catalyst particles are collected in the condensate oil asa slurry. A portion or all of this slurry may be returned to thereaction zone 22 as recycle through line H.

Below the reaction vessel 23 and the discharge end 16 of the inlet pipeIf) an enlarged chamber 46 is provided in the bottom portion of thevessel 23 for receiving the catalyst particles from reaction zone 22. Asthe spent catalyst leaves the bottom of the reaction zone 22, it fallsinto an annular stripping zone 41 formed by cylinders 48 and 49.Cylinder 48 is spaced from and supported by the inner wall of vessel 23.Inner cylinder 49 is supported from the edge of flared discharge end [8and hangs down into The stripping zone 41 terminates above the bottom ofvessel 23. However, the vided with one or more fluidizing inlets asshown stripping zonemay be constructed and supportat 69 to introducefluidizing gas, if desired.

ed in other ways. Stripping zone 41 is provided The spent catalyst fromthe standpipe 64 is into maintain the velocity of the stripping gasestroduced into line 12 where it is mixed with a passing through zone 47above a mimmum vesuitable regenerating gas introduced through locity toobtain improved stripping The flared line 14 e regenerating gas may beany suit- Circular headers 50 are provided which suror may be hightemperature gas such as freshly gaseous hydrocarbons or other inert gasto the 15 head of fluidized catalyst in the standpipe 64 e u d a a pur ia u w n using a s 16 into the bottom portion of the regeneration theticsilica-alumina gel the use of other gases zone 18 The regeneration zone18 is provided may b p d- 20 with a perforated distribution plate 82below m the Circular headers e m which the mixture of spent catalyst andregenlet lines 53 extend into chamber 46 below stripcrating gas isintroduced. The distribution as into a ring 53a arranged below ripp nThe velocity of the gases passing through the used if desiredlevel isshown in one position in the drawing e s ipp n or pur in gas p nupwardbut may be varied if desired.

y u h the relatively dense fluidized Spent I At one side theregeneration zone is provided catalyst r C ntact particles substantiallyre with a vertically arranged baffle 86 to provide inlet line or line? 5lead to the bottom the regeneration zone 18. With the level 04 arthestripping zone 41, a sleeve 01 about the t catalyst; d i theregeneration zone. In same diameter as plate I 8 may be placed on theorder t remove large part of the entrained flared discharge end '6 t0extend ai bOVe thfi at l st particles a separating means 88:15 1 flareddischarge end I 6 for a Short distancevided in the top portion of theregeneration zone charge end 0f the inlet Pipe has an 811ml means is acyclone separator or Multi-clone the discharge end it. In this way thevelocity head through line 9g The separated solid e of the reactantsabove the discharge end I 6 of tides e collected i hopper 94 associatedthe inlet pipe I4 is maintained suflioiently high with the eparatingmeans as,

to prevent settling of the catalyst particles. If desired, the hopper 94may b provided with The stripping gas then passes upwardly throughheaders 96, manifold 98 and inlet lines I02 for the bed of catalyst andout with the vaporous reintroducing flujdjzing gas i t the hopper toused ually operated damper or valve I 08 near its lower If desired, thehopper 32 and the return pipes end The valve '08 is Operated from the 34and 35 may be provided with fluidizmg inlets terior of the unit tomaintain the pipe I06 full for introducing fluidizing In the drawing ofcatalyst at all times during the operation of Lines 58 associated withcircular headers 59 are mg gas at one or more points t maintain th forintroducilig fiuidizing g mm the solid particles in fluidized condition.

fluidizing inlet may be used. n assed to a stand 1 e The purged spentcatalyst is withdrawn from dmon Withdrawn d p p p the bottom of thechamber 46 by means of standpipe G4. The standpipe 64 is provided WltinSlide Valves 66 and 68' The bottom valve into line l2 for admixture withthe reactants in withdrawn from the reaction zone 22. Slide du d intolin e Hi Top valve I |4 ls used valve 66 is provided as a spare. In caseit is as a Fluidlzmg lines l e r v for desired to shut down t systemboth vanes r the standpipe H2 for introducing flllldlzlllg gas areclosed. The standpipe 64 may also be proat n 1' m r p nts intheistandplpe t0 m mtain the particles in fluidized condition. Air maybe used as a fluidizing gas in lines H1 and inlet lines I92 for hop-per94, especially when cracking with synthetic catalyst. Steam is preferredfor natural catalyst operation so as to reduce the quantity ofnon-condensible gases entering the reactor along with the regeneratedcatalyst. The standpipe II2 is a long apparatus and fluidizing gasintroduced into the lower half of the standpipe may be at a higherpressure than fluidizing gas introduced into the upper half of thestandpipe.

Returning now to the regeneration gases leaving the regeneration zone 18through line 92, the regeneration gases are passed through a waste heatboiler H8 which is used for recovering heat from the regeneration gaseswhile at time reducing the temperature of the regeneration gases. Thewaste heat boiler II8 is provided with an inlet I22 and an outlet I24for a cooling mediu such as water for indirect heat exchangerelationship with v the regeneration gases to produce steam. The cooledregeneration gases are then passed through line I26 and introduced intothe lower portion of a Cottrell precipitator I28 for removing the lasttraces of solid particles from the gases. Other separating means as afilter, screens or the like may be used. The gases freed of powderedmaterial are passed overhead through line I32 and may be vented to theatmosphere.

The separated solid particles are collected in a hopper I34. If desired,headers I39 may be used having a manifold I38 and inlet lines I39- forintroducing fluidizing gas into the hopper I34.

The solid particles recovered in the Cottrell precipitator areexceedingly fine and are difficult to fluidize. In order to make afluidizable mixture, coarser regenerated particles from the well 81 inthe regenerator 18 are withdrawn through line I44and introduced into thehopper I34 associated with the Cottrell precipitator. A rvalve I45 isprovided in the line;I44 for controlling the amount of coarser particlesintroduced into the hopper I34.

The mixture of fine and coarser solid particles is then introduced intoa standpipe I52 provided with slide valves I54 and I55 similar inoperation and construction to those above described. If desired,fluidizing inlets I51 may be provided for introducing fluidizing gasinto the standpipe I52 at one or more points.

The fine solid particles together with the admixed coarser particlesafter leaving the standpipe I52 are mixed with a gas such as airintroduced through line the mixture blown through line I62 and returneddirectly above the well 81 in regeneration zone 18 at the point I84.

When feed stocks are used which do not deposit sufiicient burnable'raise the temperature of the regenerated powdered catalyst or contactmaterial to the desired extent, heat is added to the regeneratedcatalyst in other ways. For example, oil may be added to theregeneration zone 18 and burned therein to increase the temperature ofthe solid particles undergoing regeneration therein. A part or all ofthe oil slurry separated with the condensate oil recovered from thereaction products as above pointed out may be injected into line 16through line I99 or into regeneration zone 18 through line I92.

Instead of using the oil slurry or in addition thereto an auxiliaryburner I94 may be used. Fuel, such as gas, is introduced into the burnerI94 through line I96. As shown in the drawing a down flow burner is usedbut other forms of burners may be used. Air to support combustion isintroduced into the top of the burner I94 through line I98. Preferablythe fuel line I98 and air line I98 are so interconnected by controlsthat the fuel is automatically turned off if the air supply is turnedofi for any reason. The air is first compressed in compressor 292 to apressure of about 10 to 15 lbs. per square inch and one part thereofpassed to burner I94 through line I98, another part thereof passed 294and line 296 to be used as the lower part of burner I94 to reduce thetemperature of the combustion gases leaving the burner I94 through line299 supplying line 14 to about 1250 F. The quench air also supplies therest of the regenerating gas for regenerating the spent catalyst in theregeneration zone 18.. A portion of the compressed air passing throughline 294 is passed through line 2 I2 to remove part of the moisturefrom. the air as will be presently described.

The hot products of combustion and air passing through line 298 areintroduced into line 12 through line 14. In this, way heat is added tothe regeneration zone and to the heat of regeneration and the contactparticles are heated to a temperature of about 1050 F. to 1200 F. sothat the contact particles will have a sufficiently high temperature toheat the reactants and also to supply the heat of reaction. In casesWhere the auxiliary burner I94 is not needed regenerating gas atordinary temperature may be introduced through line 14 into line 12.

The portion of the air passing through line 2I2 is passed through acooler 2I4 having an inlet 2IB and an outlet 2I8 to remove heat ofcompression and to reduce the temperature of the compressed air to about10 F. to F. At thi temperature water is condensed and collected in dripdrum 222 into which the cooled compressed air is introduced. Water isremoved from drum 222 through valved outlet 224 and the partially driedair leaves the top of the drum through line 2 26.

In certain cases tively dry air for use as a fluidizing means or as ameans for transferring relatively c001 powdered material as will behereinafter described. The compressed air is not completely dried buthas been cooled to a temperature lower than will be encountered in theprocess and therefore no condensation of water will result when thedried air is mixed with relatively cool powder.

desired for any reason to shut down the unit, the fuel to the auxiliaryburner turned off but not the air, and feed of reactants to the unit isturned off. The valves at the bottom of standpipes H2 and I52 areclosed. The reaction zone 22 is purged with steam introduced from line5! through line 53 adjacent stripping zone 41, line 53' entering thebottom portion of chamber 46 and line 221 which leads into the bottomportion of an upwardly directed tube 228 forming an extension of feedline I9. Then as much as possible of the catalyst from the reac tionzone 22 is emptied into the regeneration zone 18 via standpipe 84 andlines 12 and 1B. The vent line 28 from reaction zone 22 is shut 01f tothe fractionating equipment in any suitable manner and the dust ladengas is passed to the Cottrell precipitator through valved line 229.

The steam lines 5| and 221 are then closed and air is passed into line228 through line 232 and through line 228 leading to lines 53 and 53from line 298. Valves II4 and H6 in stand- I94 is pipe I I2 are thenpartly opened to permit recycling of catalyst at a low rate from thereaction material is sent through a cooler 254 where it is in indirectheat exchange with a cooling medium h it is removed by a star feeder 218 to a conveyor 282.

The conveyor 282 has a means diagrammatigenerator Well 81.

Storage hopper 264 is provided with aeration lines 302 for introducingfiuidizing gas into the When all powdered material is removed from theunit the flow of all gas is stopped to the hoppers.

The feeding of reactants to the unit will now safety valve connectionMB.

In Fig. 3 it will be seen that oil is pumped through line H that is,they point downstream.

Another set of nozzles 336 is provided having branch lines II forfeeding 011 slurry or cycle oil into the catalyst or contact particlespassfiner and containing about 5% to 25% of particles having a sizebetween 0 and 20 microns.

In the catalytic cracking of a reduced crude oil the crackingtemperature in the reaction sing of the lines might occur. Therefore, itis zone is about 980 F. and the regeneration tam- 'tgessiae--=:perature* is "abut= 1100'- F. With the; reduced heated to atemperature ctr-1005 F. and" in order to supply the heat of vaporizationand ofcracking a-mixture of inert solid particles and: catalystparticles is used.- The ratio ofsolid material to the -crude-oil-byweight is about 25 to l. -The'1catalyst is included-in this solid to oilratio and :theamount of" catalyst 93111 13118 mixture is aboutin-the'proportionr of 9 to 1' part of:oil;'by Weight. Thevelocity of thevapors and gases-inwthe-i reaction zone and the are'generation-zone isabout 1.5 feet per second. With'this velocity the fluidized mixture inthe 'reaction zone*22 has a'density of about 10 to v' poundstper'cubic'foot and the density of the suspension above the catalyst bed. ismuch sxnallen -decre'asing'to about 0.002 to 0.01pound peri-cubic' footat the cyclone-inlet; The regenation zone isxmaintainedaunder apressureof bout l poun'dper squaresinch: gauge and the reaction-zone ismaintained under a pressure 1" ofi'about 9 pounds per square inch gauge.Jrhe -reason for. maintaining the reaction-zone unaiderl a s1ightpressure'- pressure to overcome pressure drop-throughithe -outletlines-and fractionating or other .equiplment usedv to 'recover gasolineand other- 'fract'ions.

ln anothei example a relatively- "lightwgas oil is -used for producingaviation gasoline. 1 A light 1 East' Texas gas oil-having a 37 A. P. Lgravity, mid-boilingpoint otab'ou't 5e0-F. and azfinal "11mg pointof-about 700 is preheated to after =-having*-passed through heat rs notshown m'the drawing The i""preheated"gas oil is' r'n'ixed with the"hot-"regenefated' catalyst which is at a sumcienuy -m h temperature toheat'andvaporize-thwarts oil and tom'aintain it' at the'conversiontemperature 'desir'ed." In thiscase no solid inertmaterial is added tothe'catalyst and'onlycatalyst 1" particles" areused. In" some cases;however, in-

ertsolid particlesmay be added. ""The catalyst is fin'elyfiividedforfn'en'dhas particles of a size offioo tof400' standard'i esh offinerITThe; catalyst may be 'any' suitable ,cra'cking' catalyst but'for" the production of'avianon gasoline a synthetid'gelcatalysficontainfi ling silica" and "ammma or silica and magnesia spreferred 2m order to supply the necess'aryheat or vaporizatior'i'andTof cracking and to obtain" about conversion of the gas'oil' toaviation'g'asoline about 7.5 parts of catalystbonip'r'ising" thesyntheticgel silica aluinina, to 'oriepa'rt of oil Thy Wi'ghtiare used!'Th'etmperature i zluring cracking is-QbbuF'TOO" F. to about" 850F.""Ihe fluidized mass of catalyst particles iri' thereaction zone'2 2has a density of about" 12' to 16 pounds per cubic foot and the velocityor the aporous products leaving-the reaction zone 2 is about -1 to Meetper second.

The velocity of the regenerating-gas. in. re-

generation zone 18 is about 1 1301.5 feet per'sec- 6 ond and with thisvelocity-the catalystparticles in the/regeneration zone are maintainedin the fiIITdiZBd- COIl-dlblOHfiJld have a density of about 12 to 16pounds per cubic foot. Due to the tur- ---bulent "condition ofthecatalyst particles in the regeneration zone thetemperature during.regeneration is maintained substantially uniform throughout thefluidized mass and is about l050 F. Thehotregenerated'catalyst at aboutl050 F. flows down the standpipe H2 and is directly is to r provide-1sufficient 12 r remixedfwitiiltnejiight gas "m1: to. supply heat of 1vaporization" and heat of; reaction" or conversion. Whilevcertainalel'ocitiesihave been given; for theyapors leaving the reaction zone 22and the 5 rre'generationsgas: leaving the regeneration zone t sbeunderstoodthat others/e ocities 'iima'fyl be used between 1 94130110 0.5and 1:5 feetper Y second. 1' The regeneration temperaturestmay be-va'rie'dlbut" 'Whemaci'd treated. bentoniteiclays-are 10 1; used thetemperature during regeneration is prefer'ably rnaintained below about1200." Higher regeneration -te- 'p'eraturesthane1-200 Fsmay be i usedwith "'syntlieti c gelcatalysts. -When i1"sing ghigl' er regenerationtemperatures;- 1ess catalyst or solid particle's"will-be'necessaryfor-vaporizing the 'ga'sfoil' oiLotherIBediand maintaining it atth'reactidn temperature. a v With the nozzles r3l2 arranged as shownfil'Fig. t 2 the nozzles are surroundd'by' a stream of' lsolid particlesinepipe 14-. to preventfspl'ashing of the liquid toil againstrthe wallofspipel M where coke deposits might-formant]. so as to preventtheaccumulationiof liQlll'dnOll-lfl any part ofsrthe re- 25 actor inletline I 4. 7

- In thee examples' 'given-sabove-sthe conditions vii rnay bevariediwithoutaiepartirigrtrom theispirit ot the' invntion.

' -"While-the invention has beemparticularly oescribedin-thef exam iesin 'conriection with catalytic cracking orhydro'carbonbil's, it isto-benn- ""deistood that it'may beuse'd. inTothiWaLtztlytlc"'conver'sionsoii hydrocarbons "such as reforming, "hydrofor'ming,alkyla'tion';tpolymerizationy dehyeio' eriationg 'et'cllaridfmay also beused in Tother catalytic' reactionssuch as,-. o'xidation, reduction, I rchlorination; shale distillation, coal carbonization,

:etc

40 Whilaone: form of; apparatusihasrbeenishown in the drawing andspecific" examples; haves-been a": given; it. i to beiunderstood' ithat1311688 31 9 by "--way of illustrationzionlyandyari'OuS changesmnd -IIf6d'lfiCas1-iiOllS** may be made 'ii i'thout departing fi orn thespirit or theinve'ntion.

"*This application is' frled" as 'a"division of our 7 application SerialNof i'l 0,-534 filedonDecmber 3011942"; nQW'Pat'entT'NG."24901798;granted Dej e'embef113r1949. 'Wh'at isclaimedis:

'='In a"liightemperature'process "using a-large amount of catalystpartlcles'for "convertin t hydrocarbon feed in thepresence, ofre'eycledufiuidi'zed' catalyst in areaction zone and regenerating "theresulting 'spe t "catalyst. as a fluidized. 'mix- "fture" in 'a're'g'eln'rationfzone and" wherein it is desired to shutdown the pr'ocess"and remove substantially allthe" -catalyst -iror'ri the "reaction fandfr'egeneration fzonesfthe improvementwhich comprisesturning-oft*the'liydrocarbon'feed;purgg mg thereactiomzone with "steam;restricting the V flow of catalyst into the reactionzone'ytransferringasr'n'uch as-possible of the catalystfrom the reaction zone to -therege'nerationzone;introducmg" a'ir intcithe reaction zone and recyclingcatalyst at a lovvi -rate between thereactiorr zone and 'thereg'eneration zone'while the catalyst is cooled by theziair to about 30015: to1500 downwardly eremovin'g ime :cata'lystiromthe;.-regeneration:zone as a dense-=fluidizedwco1umnsaddingzgasto theremoved-catalyst tostorm aglighter. suspension,-*=passing-saidzsuspension ot-catalystto -a=settling 1andustoragezoneawhich is :Ventedtoethe atmosg-phere,exhausting?dusteladerr gas from an upper portion of said storage zone, recoveringsolid ma- 2,656,466 3 I4 terial from said dust-laden gas and returningthe Number Name Date recovered solids to the storage zone. 2,337,684Scheineman Dec. 28, 1943 EDWIN J. GOHR. 2,387,309 Sweeney Oct 23, 1945HOMER Z. MARTIN. 2,391,367 I-Iodgeson Dec. 18, 1945 CHARLES E. JAHNIG. 52,393,554 Ogorzally Jan. 22, 1946 CHARLES W. TYSON. 2,396,109 MartinMar. 5, 1946 JOHN M. GRAHAM. 2,410,284 Gunness et a1 Oct. 29, 19462,440,623 Voorhees Apr. 27, 1948 References Cited in the file of thispatent 2,448,553 Schutte et a1 Sept. 7, 1948 UNITED STATES PATENTS 102,451,804 Campbell et a1 Oct. 19, 1948 6c. 13, 1949 213191590 EastmanMay 1943 2 515 374 Keith et a1 July 1 950 2,325,516 Holt et a1 July 27,1943

